1. Field of the Invention
The present invention relates to a sensing device for recognizing a substance to be sensed contained in a sample solution and determining its quantity based on an oscillation frequency of a piezoelectric resonator such as a quartz-crystal resonator.
2. Description of the Related Art
As a sensing device detecting a trace amount of a substance contained in a sample solution, there has been known a quartz-crystal sensor utilizing a quartz-crystal resonator, and a detection principle of such a quartz-crystal sensor is that an oscillation frequency (resonance frequency) of the quartz-crystal resonator changes when it adsorbs a trace amount of a substance. For example, in such a quartz-crystal sensor, an adsorption layer made of a biological substance film or the like that recognizes a specific substance to be sensed to react therewith is formed on a front surface of a metal electrode (excitation electrode) provided on a quartz-crystal piece. When the adsorption layer is brought into contact with the sample solution, the adsorption layer reacts with the substance to be sensed contained in the sample solution to adsorb the substance to be sensed, resulting in a mass change in the adsorption layer. Since a natural frequency of the quartz-crystal resonator changes according to the mass change of the adsorption layer, the concentration of the substance to be sensed is measured by using this action. As the biological substance film, a film of an antibody reacting with a specific antigen (substance to be sensed) is used, for instance, and this film of the antibody adsorbs the antigen.
A patent document 1 proposes a sensor of a flow-through cell type using a quartz-crystal resonator. In this sensor, the quartz-crystal resonator in which an electrode is formed is provided via silicon rubber between a support substrate and a cover having a solution inflow channel and a solution discharge channel. In the silicon rubber, a hole portion for storing a solution is formed, and a flow-through cell is formed by the cover, the quartz-crystal resonator, and the silicon rubber, and the solution supplied from the inflow channel is discharged from an outflow side after flowing onto the electrode of the quartz-crystal resonator to come into contact with the electrode. Being capable of continuous supply of a liquid, such a sensor of the flow-through cell type has advantages that a frequency characteristic can be easily stabilized, the liquid can be smoothly replaced, and only a small amount of a sample solution is necessary.
In developing a sensing device using a quartz-crystal sensor of such a flow-through cell type, the present inventors have studied the configuration of a system having high processing power and capable of high-accuracy measurement. Though describing the structure of the sensor of the flow-through cell type, the patent document 1 does not describe how the above object is achieved and therefore, the above object cannot be achieved even by the patent document 1.
[Patent document 1] Japanese Patent Application Laid-open No. Hei 11-183479